Category Archives: Electronics - Page 32

ARRL and amp work

Posted by sm2wmv on March 9, 2011 Comments Off

This weekend I had a visit from SM3WMU and SM3RAB that worked some in the ARRL DX SSB contest. SM3WMU worked SB 20 while Ulf, SM3RAB tried to do 40m. The propagations were not very good on Saturday, especially 40 just brought about 30 qsos but on Sunday morning the propagations were a lot better and Ulf ended up with about 230 qsos. Tomas, SM3WMU did 1200 qsos on 20m but since they both left on Sunday during the day a lot of hours were missed with the best propagations of the weekend. So I did join the contest with the SM2WMV callsign and had my best high rate hour ever, 270 qsos! I worked 630 qsos during about 3.5 hours, 600 of them on 20m.

Today I put together a new server for SJ2W. The old one is a 650 MHz with 512 MB RAM which has been working well, but I want to try having all the remote software on the server instead of having another computer on the whole time. So I upgraded to an Athlon X2 3 GHz with 4 GB RAM, which makes it possible to run Ubuntu as a root system while being able to boot up Windows XP in virtualbox.

I also did some amp work today, I soldered some control cables and added the two power supplies, one for 5V and the other for 24V. I need to build a step down converter for 12V as well from the 24v power supply.

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Rotator control from openASC

Posted by sm2wmv on March 1, 2011 Comments Off

I’ve done some more work on the openASC project. A lot of new software has been written, including band interlock, some small bug fixes, more error handling, better support for rotators and more stuff that I don’t remember. I also intend to fix the rotation so that it works properly, so I took with me an KR-400 rotator that SE2T donated and modified it by putting in one of my openASC rotator boards. This board is basically just a micro-controller with a bus interface and some relay drivers and analog inputs (also digital inputs for pulse sensing). An external board is also used with relays that act as “digital” fingers pushing the buttons on the box. It is still possible to control the antenna manually if wanted.

When this works I will put rotator boards into all rotators. However the 60m tower need to wait until it has got its end stops, so that a computer bug doesn’t make it rip of all cables etc.

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More done on the 2x4CX1500B amplifier

Posted by sm2wmv on February 18, 2011 Comments Off

Today I did some more work on the amplifier. I milled out a sensor card, which will be used to sense the control and screen grid currents. It can also measure the voltage of the screen and all this is fed into the controller boards A/D converter. I also milled a couple of couplings, which will connect the stepper motors to the potentiometers that measures the position of each vacuum capacitor. While milling the sensor board I also milled out the high voltage pickup board, used to measure the voltage from the 2.5kV HV transformer for the anode. I also mounted some of the control electronics.

Now the next step will be to start adding the control cables for the vacuum relays to the proper positions of the control system. I will also soon mount the potentiometers which will make it possible for me to start testing the stepper motors, which will be a blast.

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PI-tank almost done

Posted by sm2wmv on February 7, 2011 Comments Off

I’ve almost gotten the PI-tank completed now on the 2x4CX1500B amplifier. I also added some padding capacitors for the C2 cap, so we can get up to 4200 pF of total capacitance on the C2. I also added feed-through capacitors to all the vacuum relays and the stepper motors.

The next step is to mount the potentiometers for the stepper motors, so we can know exactly the position of the capacitors, and no need to count steps of the motors. I also ordered some current sensor transformers which will be used to sense the current to the control and screen grid. For measuring the current from the anode I will just use a resistor and measure the voltage drop over it (at the cathode side).